The statistics say that most collections will produce some non-fertile and degenerate embryos. If your donor has an unusually large percentage of these nonviable embryos, we make sure we address the issues that can cause this effect. The first variable to evaluate is semen quality. Obviously, high quality semen is essential to the success of ET. However, I do believe semen always gets the blame! Be sure your semen is evaluated preferably prior to using in a flush. Just like donor variability in fertility, there is much variation in the ability of bulls to produce viable embryos. If you have any doubts, especially on semen collected from young, highly conditioned show bulls, have your semen evaluated. Also be sure your semen handling techniques are sound. Consistently check your thermometer to assure accuracy. Many other factors affect embryo quality. Stress (hot weather, injury, temperament). Always try to minimize stress in your donors and recips. Finally, there is certainly an inherent genetic predisposition in some donors that make them poor candidates for ET programs. All cows do not produce viable embryos.
The key to the usefulness of this program is accurate heat detection in the recipients. This will not work if you are not able to accurately identify return heats on your recips. I schedule flush days every 35-40 days. This allows you time to check for heats in your recips that are used. Most of those heats will be 12-16 days after transfers (19-23 days from heat). The 35 day interval will allow you time to resynchronize those open recips for the next flush in addition to the recips that are not used or are new to the program. This protocol will greatly reduce the time your recips will stay open and give them more opportunities to get pregnant in an acceptable window of time. The greatest expense in any ET program is the recips. It is very important to maximize pregnancy rates in your pool of recip cows. This program allows you to produce a higher percentage of ET pregnancies in your herd. If heat detection in the recips that have embryos transferred into them is not an option, we can pregnancy check those cows and resynch the open cows on the next cycle. That will still allow you to reuse those recips in a shorter window of time but is obviously not as good as the first plan. What is the best way to synchronize your recips, you might ask. We currently use two primary protocols. When we utilize heat detection programs, we recommend the Select Synch + CIDR (GnRH + CIDR followed in 7 days by CIDR removal + Prostaglandin injection). Recips are then heat detected and time of standing heats are recorded. Only the recips with recorded heats are then checked on transfer day. We commonly use Fixed Time ET (FTET) Programs now eliminating the need for heat detection. The protocol we use is Co-Synch + CIDR. The protocol is the same as for heat detection except the recips are also given a dose of GnRH (Cystorelin, Factrel, Fertagyl) 48 hours after CIDR removal and Prostaglandin injection. All recips are then brought through the chute on transfer day. Typically, we will use approximately 80% of the recips synchronized.